KR100689437B1 - Receiver and method for determining timer value for detection of missed frame in a mobile communication system employing radio link protocol - Google Patents

Abstract

The present invention does not use a fixed REXMIT_TIMER, but more clearly grasps the actual communication environment and calculates the REXMIT_TIMER value for the situation so that FRAME performs the optimal retransmission process. To this end, the present invention determines the communication environment of the current state, calculates the optimal REXMIT_TIMER value and uses the optimal REXMIT_TIMER value as a criterion for determining the missed frame.

RLP

Description

RECEIVER AND METHOD FOR DETERMINING TIMER VALUE FOR DETECTION OF MISSED FRAME IN A MOBILE COMMUNICATION SYSTEM EMPLOYING RADIO LINK PROTOCOL}

1 illustrates a data communication system constructed in accordance with an embodiment of the present invention;

2 is a block diagram of a receiving apparatus according to the present invention;

3 is a block diagram illustrating an RLP processing unit according to an embodiment of the present invention;

4 is a diagram illustrating a control flow when data is received by an RLP processing unit according to an embodiment of the present invention;

5 is a diagram illustrating a control flow when updating a REXMIT_TIMER value according to the first embodiment of the present invention;

6 is a diagram illustrating a control flow when updating a REXMIT_TIMER value according to a second embodiment of the present invention;

FIG. 7 is a diagram schematically illustrating a case where a REX_COUNT value is calculated for each time section. FIG.

The present invention relates to a receiving apparatus and method for determining a timer value for detecting a missed frame in a mobile communication system employing a radio link protocol.

In general, the code division multiple access mobile communication system has evolved from the IS-95 standard, which mainly focuses on voice, to the cdma2000 standard, which enables high-speed data transmission as well as voice. In the cdma2000 standard, services such as high quality voice, moving picture, and internet search are possible.

In such a CDMA mobile communication system, a radio link protocol is used to solve data corruption in a wireless environment. The radio link protocol uses NAK based on an Automatic Repeat Request (ARQ) scheme to recover an error occurring on an air channel. That is, when the receiving end RLP detects an unreceived RLP frame, the receiving end RLP transmits a NAK frame requesting retransmission of the corresponding frame to the transmitting end RLP, and the receiving end RLP transmits the requested frame. And, the radio link protocol is based on a frame having a length of 20 ms at a transmission rate of 9.6 kbps or 14.4 kbps or less.

Accordingly, the types of FRAME received and received in RLP DATA communication can be largely divided into NEW FRAME and RETRANSMISSION FRAME. That is, it is a new frame for new data transmission and a retransmission frame for retransmission at the sender according to the NAK frame sent by the receiver when such transmission fails.

When the receiving side is estimated to generate an unreceived FRAME, as described above, the receiving side transmits a NAK FRAME including the unreceived FRAME sequence to the calling party. Here, the value used by the receiver to estimate the occurrence of an unreceived frame is REXMIT_TIMER. If the receiving side does not receive a FRAME while receiving the FRAME sequentially, the receiver does not request to retransmit the FRAME immediately by using the NAK FRAME, but waits longer to receive the FRAME of REXMIT_TIMER unit, and if it does not arrive, the MISSED FRAME The sender requests the sender to retransmit the MISSED FRAME including the SEQUENCE of the MISSED FRAME in the NAK FRAME.

REXMIT_TIMER is a constant value calculated from the RLP_DELAYs value. The RLP_DELAYs value is calculated in one of two ways. In the RLP SYNC EXCHANGE PROCEDURES process, the RTT (Round Trip Time) value obtained from the ROUND TRIP DELAY value or assigned as a constant value from the base station is used as the RLP_DELAYs value. The receiver finally determines the missed frame based on the fixed REXMIT_TIMER value and retransmits it accordingly.

The RLP LAYER on the receiving side decreases the REXMIT_TIMER value for the RLP frame that has not been received each time a normal NULL, IDLE or NEW frame is received. If the value reaches 0, the FRAME is regarded as a MISSED FRAME and the FRAME is processed for retransmission. Rough

The terminal moves during the data communication or the communication environment and its state change from time to time due to changes in the surrounding environment. However, the UE fixedly uses the REXMIT_TIMER value obtained from the constant value RLP_DELAYs calculated in the RLP SYNC EXCHANGE PROCEDURES that is part of the INITIALIZATION process until the next INITIALIZATION process occurs. Alternatively, the terminal uses the RTT value of the RLP_BLOB FRAME as RLP_DELAYs in RLP_BLOB, which is also part of the INITIALIZATION process, and also calculates the REXMIT_TIMER value from the RLP_DELAYs. Will be used for.

Due to the use of this constant value of REXMIT_TIMER, the terminal does not react sensitively to the changed surrounding environment, and in a situation where the user waits for a long time unnecessarily or waits for a longer time, an unnecessary and inappropriate retransmission request is required.

This completely ignores the characteristics of the wireless communication environment which is more affected by the environment than any other communication. The REXMIT_TIMER value must be changed to adapt to the environment.

Accordingly, the present invention provides a receiving apparatus and method for adaptively determining a timer value for detecting a missed frame in an actual communication environment in a mobile communication system employing a radio link protocol.

In order to achieve the above object, the present invention provides a method for determining a timer value for detecting a missed frame in a receiving apparatus of a mobile communication system employing a radio link protocol, wherein the number of frames requiring retransmission is counted. And updating a timer value for detecting the lost frame with reference to the count value.

In addition, the present invention provides a method for determining a timer value for detecting a lost frame in a receiving apparatus of a mobile communication system employing a radio link protocol, wherein the number of frames for requesting retransmission is counted for each time interval. And updating a timer value for detecting the lost frame with reference to the count value for each time period.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention does not use a fixed REXMIT_TIMER, but more clearly grasps the actual communication environment and calculates the REXMIT_TIMER value for the situation so that FRAME performs the optimal retransmission process. To this end, the present invention determines the communication environment of the current state, calculates the optimal REXMIT_TIMER value and uses the optimal REXMIT_TIMER value as a criterion for determining the missed frame. The present invention counts the number of FRAMEs that require retransmission to determine the current communication environment. Counting of this retransmission request frame may be included in a NAK LIST PROCESSING process or a process for creating a NAK frame. That is, the present invention counts the number of FRAME SEQUENCE that requires retransmission every time and uses the value (hereinafter referred to as REX_COUNT).

According to an embodiment of the present invention, the REX_COUNT value is updated at every unit time of making the FRAME (20 ms units for FCH and SCH), and the REXMIT_TIMER value is maintained as INCREMENT, DECREMENT or the current value depending on the range of the REX_COUNT value. Select one and update it.

According to another exemplary embodiment of the present invention, the REX_COUNT value is checked for each time interval, and the REX_COUNT value for each time interval is compared with each other, and one of increasing, decreasing, or maintaining the current value is selected according to the comparison result. UPDATE

 A data communication system constructed in accordance with an embodiment of the present invention will be described with reference to FIG. As shown, subscriber station 102 communicates with network 108 via wireless communication channel 104 and base station 106. Subscriber station 102 and base station 106 establish a radio link protocol (RLP) communication link to carry a stream of data bytes over wireless communication channel 104. The data bytes exchanged between the subscriber station 102 and the network 108 through the base station 106 may be Internet Protocol (IP) datagrams converted into a byte stream using a conversion protocol such as Point-to-Point Protocol (PPP). have. IP and PPP protocols are known. Before any data is exchanged between subscriber station 102 and base station 106, an RLP link between the two must be established. RLP link establishment involves setting a round trip time (RTT) to be used by both subscriber station 102 and base station 106 for NAK timing. In general, the REXMIT_TIMER value is determined from the RTT value. As described above, the REXMIT_TIMER value is used to determine the MISSED frame when the receiving device receives the frame transmitted from the transmitting device.

Conventionally, the REXMIT_TIMER value obtained from the RTT value in this initialization process is used until the RTT value is newly set in the next initialization process. On the other hand, the present invention more clearly grasps the actual communication environment and calculates the REXMIT_TIMER value for the situation so that the FRAME performs the optimal retransmission process. According to the present invention, if the current communication situation properly receives a normal FRAME better than the previous communication situation, the reception apparatus lowers the REXMIT_TIMER value to reduce unnecessary waiting and requests retransmissions quickly. And if the receiving device receives a lot of INVALID FRAME such as missed frame, erase frame, and so on, the current reception state is poor, so the REXMIT_TIMER value is increased to increase the waiting time of the frame.

Accordingly, the reception apparatus according to the present invention can calculate the REXMIT_TIMER value suitable for the actual communication environment without using the fixed REXMIT_TIMER, so that the FRAME can perform the optimal retransmission process. Next, the hierarchical structure of the receiving apparatus according to the embodiment of the present invention will be described.

2 shows a configuration of a receiving apparatus according to the present invention, and shows only the configuration related to the present invention.

Referring to FIG. 2, the reception apparatus 200 includes a RLP processing part 210 and a PHY processing part 220. The physical layer processor 220 decodes the received frame upon reception of the frame data and transfers it to the RLP processor 210. When the decoding frame is received, the RLP processing unit 210 of the receiving apparatus checks a sequence (SEQ) number of the received decoding frame. If the sequence number of the decoding frame received from the physical layer processing unit 220 is the same as the order of the transmitted frames, it is transmitted to the upper layer. Specifically, it is assumed that the transmitting device sequentially transmits frame data in the order of sequence numbers 1, 2, 3, and 4. Then, the RLP processing unit 210 of the receiving device 200 transmits the sequence number of the frame, which has been successfully decoded from the physical layer processing unit 220, to 1, 2, 3, and 4 to the higher layer. However, there may occur a case where a specific number of sequence numbers of the received frame is not received. For example, if only two or four received sequence numbers are received, the RLP processing unit 210 of the reception apparatus 200 may confirm that there are at least two frames that have failed decoding in the physical layer processing unit 220. That is, it can be seen that an error has occurred in the frames of sequence numbers 1 and 3.

In this case, when the frame of sequence number 2 is received while the frame of sequence number 1 is not received, the RLP processing unit 210 temporarily stores the frame of sequence number 2 in a buffer, and receives a timer for the frame of the unreceived sequence number 1. Set (REXMIT_TIMER). Similarly, when a frame of sequence number 4 is received while the frame of sequence number 3 is not received, the RLP processing unit 210 temporarily stores the frame of sequence number 3 in a buffer and sets a timer for the frame of the unreceived sequence number 3. Set it. Here, different timers are set for each unreceived frame. That is, each timer REXMIT_TIMER for an unreceived frame operates differently in time as a separate timer. On the other hand, the value of each timer REXMIT_TIMER for an unreceived frame is the same and accordingly the waiting time of each frame is also the same. The present invention dynamically sets a timer value set for this unreceived frame according to the current communication situation.

To this end, the RLP processing unit 210 outputs a REX_COUNT value that counts the number of FRAMEs requesting retransmission. Here, REX_COUNT is a variable that stores the number of FRAME SEQUENCEs that require retransmission. The RLP processing unit 210 may perform count processing of the retransmission request frame in a NAK LIST PROCESSING process or a process of creating a NAK frame.

According to the first embodiment of the present invention, the RLP processing unit 210 updates the REX_COUNT value at every unit time for making the frame (20 ms unit for FCH and SCH), and sets the REXMIT_TIMER value according to the range of the REX_COUNT value. Select and update either Increment, Decrease, or Keep Current Value.

According to a second embodiment of the present invention, the REX_COUNT value is checked for each time interval, the REX_COUNT value for each time interval is compared with each other, and either the REXMIT_TIMER value is increased, decreased or the current value is selected according to the comparison result. To update.

Accordingly, the RLP processor 210 may determine the missed frame based on the optimal REXMIT_TIMER value. The RLP processing unit 210 stores the received frame in a predetermined buffer, specifically, a queue, and, for example, when receiving the frame of sequence number 1, transfers the frames of sequence number 1,2 to a higher layer. Of course, when the RLP processing unit 210 receives a frame of sequence number 3, the RLP processor 210 transfers the frames of sequence numbers 3 and 4 to a higher layer. The RLP processing unit 210 may be configured as shown in FIG. 3.

3 is a block diagram of an RLP processing unit 210 according to an embodiment of the present invention. Referring to FIG. 3, the RLP processing unit 210 includes an RLP controller 212, a reception data buffer 214, a REX_COUNT 216, and a REMIT_TIMER 218. The RLP controller 212 performs an operation of the RLP processing unit 210. In particular, since the RLP controller 212 performs an operation according to the first and second embodiments described in detail below according to the present invention, the detailed description thereof will be omitted.

The retransmission counter (REX_COUNT) 216 counts the number of FRAMEs requiring retransmission and provides the corresponding REX_COUNT value to the RLP controller 212. The retransmission timer (REMIT_TIMER) 218 is composed of one or more timers that are set when an unreceived frame is detected by the RLP controller 212. Finally, the receive data buffer 214 stores a frame for the RLP controller 212 to forward to the upper layer. Since the frames are not received in the order of sequence numbers as described above, when a frame preceding the sequence number of the unreceived frame is received, it is stored in the received data buffer 214.

Next, the control flow at the time of data reception in the RLP processing unit 210 according to the embodiment of the present invention will be described with reference to FIG. 4.

Referring to FIG. 4, the RLP processing unit 210 maintains the standby state in step 302. Here, the standby state refers to a state that waits for an event requiring a specific operation to occur. In operation 304, the RLP processor 210 checks whether a frame is received. When the RLP processing unit 210 receives the frame, the RLP processing unit 210 proceeds to step 306 to check whether the frame on which the timer is driven is received. The timer driving frame refers to a frame in which a timer is set in order to determine whether the frame is not received by the RLP processing unit 210 and determine whether the frame is a missed frame. If the RLP processing unit 210 receives the frame that is driving the timer, the RLP processing unit 210 proceeds to step 314.

If the received frame is not a timer-driven frame, the RLP processing unit 210 proceeds to step 308 to check for an unreceived frame. As described above, the RLP processing unit 210 may check the new unreceived frame by looking at the sequence number of the received frame. If there is a new unreceived frame, the RLP processor 210 proceeds to step 312 to set a timer for the new unreceived frame and proceeds to step 314. If there is no new unreceived frame, the RLP processing unit 210 proceeds to step 314. The RLP processing unit 210 stores the frame received in step 314 in a buffer.

On the other hand, the RLP processing unit 210 checks whether the frame is received in step 304, and if it is determined that the frame is not received in step 304 proceeds to step 320. The RLP processor 210 checks whether a retransmission condition occurs in step 320. For example, the RLP processing unit 210 checks whether a timer timeout occurs. As described above, the timer is set by the RLP processing unit 210 for the unreceived frame. When the timer times out, the RLP processing unit 210 determines that the frame is a MISSED FRAME and requests retransmission to the transmitting device. Done. Therefore, if the timer timeout occurs, the RLP processing unit 210 proceeds to step 322 and requests a retransmission to the transmitting device for the corresponding frame. Subsequently, the RLP processor 210 proceeds to step 324 and increments an REX_COUNT value that counts the number of FRAMEs requesting retransmission. Subsequently, the RLP processing unit 210 checks whether a timer change condition occurs in step 326. In general, if the current communication situation is good, the FRAME will be properly received, so the REX_COUNT value will be lower as the number of FRAMEs requiring retransmission is small. And if the current communication situation is poor, the reception of INVALID FRAME such as MISSED FRAME, ERASE FRAME, etc. will increase, so the REX_COUNT value will have a high value as the number of FRAMEs requiring retransmission is large.

According to an embodiment of the present invention, the RLP processing unit 210 checks whether a timer change condition has occurred based on the REX_COUNT value. If the timer change condition occurs, the RLP processing unit 210 proceeds to step 328 and updates the timer REXMIT_TIMER value to suit the current communication environment. If the current communication situation is good, the RLP processing unit 210 lowers the REXMIT_TIMER value so as to reduce unnecessary waiting and request retransmission quickly. If the current communication situation is poor, the RLP processing unit 210 increases the REXMIT_TIMER value to increase the waiting time for the corresponding FRAME.

Hereinafter, a control flow in the case of updating a REXMIT_TIMER value of a timer according to the first embodiment of the present invention will be described with reference to FIG. 5. In the first embodiment of the present invention, the REX_COUNT value is updated every unit time of making the FRAME (20 ms units for FCH and SCH), and the REXMIT_TIMER value is incremented and decremented according to the range of the REX_COUNT value. Alternatively, choose to keep the current value and update it.

However, in the real network, when FRAME is not received, retransmission always occurs in 20ms units, and REXMIT_TIMER is also used every 20ms units. Since the REXMIT_TIMER must maintain a value sensitive to the retransmission situation, the control flow of FIG. 5 according to the first embodiment is performed every 20 ms. Of course, the control flow of FIG. 4 may be performed at a period other than 20 ms.

Referring to FIG. 5, the RLP processing unit 210 first checks whether a retransmission condition occurs in step 410. For example, the RLP processing unit 210 checks whether a timer timeout occurs. As described above, this timer is a timer set by the RLP processing unit 210 for the unreceived frame. When the timer times out, the RLP processing unit 210 determines the frame as a MISSED FRAME. It will be appreciated by those skilled in the art that other conditions may cause retransmission conditions of the frame. If the timer timeout occurs, the RLP processing unit 210 proceeds to step 420 and increments the REX_COUNT value that counts the number of frames to request retransmission. Subsequently, the RLP processing unit 210 checks whether the REX_COUNT value is less than 5 in step 430. Specifically, the RLP processing unit 210 checks whether the REX_COUNT value is smaller than the first predetermined value (5 in this embodiment) since the FRAME retransmission will not occur if the current communication situation is good.

 If the REX_COUNT value is less than 5, the RLP processing unit 210 proceeds to step 440 to decrement the REXMIT_TIMER value. That is, if the current communication situation is good, the RLP processing unit 210 lowers the REXMIT_TIMER value so as to reduce unnecessary waiting and to quickly request retransmission. Of course, it is apparent that the RLP processing unit 210 may change the REXMIT_TIMER value by a predetermined range.

If the REX_COUNT value is not less than 5, the RLP processing unit 210 proceeds to step 440 and checks whether the REXMIT_TIMER value is greater than or equal to 20. If the current communication situation is poor, since retransmission of the frame will increase due to INVALID FRAME such as MISSED FRAME and ERASE FRAME, it is checked whether the REX_COUNT value is greater than or equal to the second predetermined value (20 in this embodiment). Subsequently, if the REX_COUNT value is greater than or equal to 20, the RLP processing unit 210 proceeds to step 460 to increment the REXMIT_TIMER value. That is, if the current communication situation is poor, the RLP processor 210 increases the REXMIT_TIMER value to increase the waiting time for the corresponding FRAME. If the value of REX_COUNT is less than 20, the RLP processor 210 proceeds to step 470 and maintains the value of REXMIT_TIMER unchanged. This is summarized as follows.

0 <= REX_COUNT <5: REXMIT_TIMER DECREMENT

5 <= REX_COUNT <20: Keep REXMIT_TIMER

20 <= REX_COUNT: REXMIT_TIMER INCREMENT

Next, the control flow in the case of updating the REXMIT_TIMER value of the timer according to the second embodiment of the present invention will be described with reference to FIG. 6. The second embodiment of the present invention checks the REX_COUNT value for each time interval, compares the REX_COUNT value for each time interval, and increases, decreases, or maintains the current value according to the comparison result. Select one to update.

Referring to FIG. 6, the RLP processing unit 210 first checks whether a retransmission condition occurs in step 510. If a retransmission condition occurs, the RLP processing unit 210 proceeds to step 520 and calculates a REX_COUNT value for each time interval. FIG. 7 is a diagram schematically illustrating a case where a REX_COUNT value for each time interval is calculated. Referring to FIG. 7, the REX_COUNT value is 10 in the interval 10, and the REX_COUNT value is 20 in the interval 20. That is, the RLP processor 210 counts the number of FRAMEs for requesting retransmission for each predetermined time interval. Subsequently, the RLP processing unit 210 checks whether the timer update period has arrived in step 530. This timer update period is determined so as to be sensitive to a communication situation without being loaded on the receiving device. Further, the timer update period is preferably larger than 20 ms, which is the timer update period in the first embodiment, and has a time range in which several frames can be received.

If the timer update period has arrived, the RLP processing unit 210 proceeds to step 540 and checks whether the REX_COUNT value of the current section is smaller than the REX_COUNT value of the previous section. In the example of FIG. 7, if the current section is the section indicated by 20, the RLP processing unit 210 compares the REX_COUNT value in section 20 with the REX_COUNT value in section 10. If the REX_COUNT value of the current section is smaller than the REX_COUNT value of the previous section, the RLP processor 210 proceeds to step 550 to decrease the timer value. That is, the RLP processing unit 210 determines that the number of retransmissions is reduced due to a good communication situation, and reduces the timer value so as to reduce unnecessary waiting and to request retransmissions quickly.

If the REX_COUNT value of the current section is not smaller than the REX_COUNT value of the previous section, the RLP processor 210 proceeds to step 560 to determine whether the REX_COUNT value of the current section is greater than the REX_COUNT value of the previous section. If the REX_COUNT value of the current section is greater than the REX_COUNT value of the previous section, the RLP processing unit 210 proceeds to step 570 to increase the timer value. That is, the RLP processing unit 210 determines that the number of retransmissions is increased due to a poor communication situation, and increases the wait time for the corresponding frame by increasing the timer REXMIT_TIMER value.

On the other hand, if the REX_COUNT value of the current section is not greater than or less than the REX_COUNT value of the previous section, the RLP processing unit 210 proceeds to step 580 and maintains the timer REXMIT_TIMER without changing the value.

In the second embodiment, since the timer REXMIT_TIMER value is changed for each interval, the timer REXMIT_TIMER value is described as increasing or decreasing to a certain range. However, similarly to the first embodiment, the timer REXMIT_TIMER value is changed or decremented. It will be apparent to those skilled in the art.

The present invention can be applied to any communication system that utilizes the transmission of byte streams over a wireless channel.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

As described above, the present invention does not use a fixed REXMIT_TIMER, and more accurately grasps the actual communication environment, calculates the REXMIT_TIMER value for the situation, so that the FRAME performs the optimal retransmission process so that it can respond sensitively to the communication situation. have.

Claims (11)

A method for determining a timer value for detecting a lost frame in a receiving apparatus of a mobile communication system employing a radio link protocol, Counting the number of frames requesting retransmission; And updating a timer value for detecting the lost frame with reference to the count value. 2. The method of claim 1, wherein the updating step is to decrement the timer value if the count value is less than a first threshold value. 3. The method of claim 2, wherein said updating step comprises incrementing said timer value if said count value is greater than or equal to a second threshold value. 4. The method of claim 3, wherein said updating step maintains the timer value if the count value is greater than the first threshold value and less than the second threshold value. A method for determining a timer value for detecting a lost frame in a receiving apparatus of a mobile communication system employing a radio link protocol, Counting the number of frames requesting retransmission for each time interval; And updating a timer value for detecting the lost frame with reference to the count value for each time period. The method of claim 5, wherein the updating comprises comparing the count value for each time interval and updating a timer value for detecting the lost frame according to the comparison result. The method of claim 6, wherein the updating comprises reducing a timer value for detecting the lost frame if the count value of the current time interval is less than the count value of the previous time interval. The method of claim 6, wherein the updating comprises increasing a timer value for detecting the lost frame when the count value of the current time interval is greater than the count value of the previous time interval. The method of claim 6, wherein the updating comprises maintaining a timer value for detecting the lost frame if the count value of the current time interval is not greater or smaller than the count value of the previous time interval. A reception apparatus for determining a timer value for detecting a missed frame in a mobile communication system employing a radio link protocol, A physical layer processor for decoding the received frame and transferring the received frame to a higher layer; And an RLP processing unit for counting the number of frames requesting retransmission and updating a timer value for detecting the lost frame with reference to the count value. A reception apparatus for determining a timer value for detecting a missed frame in a mobile communication system employing a radio link protocol, A physical layer processor for decoding the received frame and transferring the received frame to a higher layer; And an RLP processing unit for counting the number of frames requesting retransmission for each time interval and updating a timer value for detecting the lost frame with reference to the count value for each time interval.

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